The correct answers are:
- acid rain;
The acid rain occurs when a normal cloud gets polluters in it, so they mix, and the rain's composition is different, causing a lot of damage.
- respiratory distress;
The pollution of the air is directly affecting the respiratory system because there are lot of polluters that are toxic to the human body, so the respiratory distress is a common thing.
- global warming;
The big amounts of CO2, but also methane, released in the atmosphere, result in the increasing of the Greenhouse effect because they manage to trap more heat into the atmosphere.